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Author Topic: How do you start a jet engine?  (Read 8176 times)

Offline thedoc

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How do you start a jet engine?
« on: 20/02/2012 11:39:09 »
How does a jet engine get started?
Asked by Titus Theseira, via Facebook


                                        Visit the webpage for the podcast in which this question is answered.

 ...or Listen to the Answer or [download as MP3]

« Last Edit: 20/02/2012 11:39:09 by _system »


 

Offline thedoc

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How do you start a jet engine?
« Reply #1 on: 20/02/2012 11:39:09 »
We answered this question on the show...



 Dave -   A gas turbine jet engine is quite interesting in that it just doesn’t work unless it’s spinning - like a normal car engine.  So basically, you've got to spin it up fairly fast, so you attach an electric motor into it - either it’s integrated in there or you stick on the outside and spin it up.  Then it gets going pretty fast, you inject some fuel, then you essentially have something like a spark plug inside it which ignites the fuel, then it starts it going and it basically then starts running, spins up to full speed, and you have a jet engine.
Chris -   So it’s not dissimilar to a diesel engine in a sense that you've got to get the engine spun up to start compressing air to get it hot so you can inject fuel to start it burning, and then once it’s going, it’s got its own ability to carry itself.
Dave -   Yeah, pretty much! Also, there's nothing really to make the air explosion coming out of the back if the air is not coming in the front so you've got to have everything spinning for it to work at all.
« Last Edit: 20/02/2012 11:39:09 by _system »
 

Offline Geezer

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How do you start a jet engine?
« Reply #2 on: 24/08/2011 20:28:18 »
or, you can simply plug it into a convenient leaf blower


(DO NOT TRY THIS AT HOME!)
 

Offline chris

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How do you start a jet engine?
« Reply #3 on: 25/08/2011 09:55:29 »
I watched that video but you can't actually see anything!
 

Offline Geezer

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How do you start a jet engine?
« Reply #4 on: 25/08/2011 18:54:43 »
I watched that video but you can't actually see anything!

If I'd been holding the camera, I don't think I would have wanted to get any closer either! (It's the thing to the left connected by a large diameter flexible plastic hose.)

You could also use a hair drier to preheat it, then use compressed air to spin it up, as demonstrated in this fine piece of cinematography:


(Note the highly sophisticated, and critically important, lubrication system.)
« Last Edit: 25/08/2011 18:59:01 by Geezer »
 

Offline Bored chemist

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How do you start a jet engine?
« Reply #5 on: 26/08/2011 11:11:51 »
That's not a hair drier, it's a hot air gun. There's a difference.
 

Offline Geezer

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How do you start a jet engine?
« Reply #6 on: 26/08/2011 17:32:34 »
That's not a hair drier, it's a hot air gun. There's a difference.

I realized that, but I thought hair drier was a bit more in keeping with the overall arrangement.
 

Offline SeanB

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How do you start a jet engine?
« Reply #7 on: 26/08/2011 21:35:21 »
And you can jump start them.......... Not recommended though, as you just point the exhaust of another running one into the inlet of the non runner to spin it up enough to start.
 

Offline Geezer

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How do you start a jet engine?
« Reply #8 on: 26/08/2011 22:09:43 »
And you can jump start them.......... Not recommended though, as you just point the exhaust of another running one into the inlet of the non runner to spin it up enough to start.

I suppose if you run them downhill very fast they might start too, but I've never actually tried that, and I hope I'm never in a plane where they have to try it either  :D
 

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How do you start a jet engine?
« Reply #8 on: 26/08/2011 22:09:43 »

 

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